1. Field of the Invention
The invention relates to inspection methods and apparatus. More particularly, the invention relates to a method and apparatus for inspection of substrates to identify process and handling related defects and conditions.
2. Background of the Related Art
A chip manufacturing facility is composed of a broad spectrum of technologies. Cassettes containing semiconductor substrates are routed to various stations in the facility where they are either processed or inspected.
Semiconductor processing generally involves the deposition of material onto and removal (“etching”) of material from substrates. Typical processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, chemical mechanical planorization (CMP) etching and others. During the processing and handling of substrates, the substrates undergo various structural and chemical changes. Illustrative changes include the thickness of layers disposed on the substrate, the material of layers formed on the substrate, surface morphology, changes in the device patterns, etc. These changes must be controlled in order to produce the desired electrical characteristics of the devices formed on the substrate. In the case of etching, for example, end-point detection methods are used to determine when the requisite amount of material has been removed from the substrate. More generally, successful processing requires ensuring the correct process recipe, controlling process excursions (e.g., gas flow, temperature, pressure, electromagnetic energy, duration, etc) and the like.
In addition, the processing environment must be sufficiently stable and free from contamination. Sources of contamination include wear from mechanical motion, degradation of seals, contaminated gases, other contaminated substrates, flaking of deposits from processing chambers, nucleation of reactive gases, condensation during chamber pumpdown, arcing in plasma chambers and so forth. Such sources of contamination produce particles that contact the substrates and can result in defective devices. As the geometries of device features shrink, the impact of contamination increases. Thus, current semiconductor manufacturing routinely includes inspection of substrates for particles to identify “dirty” processes or equipment
Additionally, substrate centerfinding and orientation necessary steps during processing to generate positional information regarding substrates. In conventional systems such procedures are performed at designated locations in the processing system. Thus, a substrate must be shuttled to the designated locations in order to undergo each procedure, thereby decreasing system throughput.
Another situation which can cause increased processing costs is improper substrate routing in the chip manufacturing facility. Occasionally, a substrate may be improperly routed to a process chamber where the processing conditions cause a volatile reaction, thereby damaging the substrate and/or the processing chamber. For example, consider the case of a substrate with a photoresist layer that has been inadvertently routed to a PVD chamber. Processing this substrate in the PVD chamber is known to cause severe damage to the chamber, resulting in substantial repair and/or replacement costs. Because current processing systems are not equipped to prevent misrouting, the cost of ownership is increased.
Currently, comprehensive testing and analysis of substrates for process integrity and contamination requires the periodic or often constant removal of one or more substrates from the processing environment into a testing environment. Thus, production flow is effectively disrupted during transfer and inspection of the substrates. Consequently, conventional metrology inspection methods can drastically increase overhead time associated with chip manufacturing. Further, because such an inspection method is conducive only to periodic sampling due to the negative impact on throughput, many contaminated substrates can be processed without inspection resulting in fabrication of defective devices. Problems are compounded in cases where the substrates are re-distributed from a given batch making it difficult to trace back to the contaminating source.
Thus, what is needed is an integrated metrology and process inspection system, a “gate-keeper” apparatus and method, capable of examining a substrate for selected characteristics which include particles, processing flaws, orientation, centerfinding, reflectivity, substrate type, discontinuity, etc. as an integral part of the processing system. Preferably, such an inspection can be performed prior to, during, and after substrate processing, thereby determining real time pre- and post-processing conditions of the substrate.
Other functions routinely performed in conventional processing systems and inspection systems include calibration of robots and the inspection equipment. Current methods of calibration negatively impact throughput because the production must be halted in order to perform the calibration. Degradation usually goes undetected until a catastrophic failure occurs. A preferred processing system would include an integrated, or embedded, device capable of continuously monitoring the status of the robot and inspection system and facilitate automatic corrective action. Thus, the processing system could be further integrated and throughput can be increased. In addition, it would be preferable for such an integrated device to be capable of monitoring robot behavior. Robot behavior of interest includes acceleration, speed, repeatability, stability, etc. Additionally, it would be preferable for such an integrated device to determine the presence of contamination on the robot blade which supports substrates during transfer. The presence of such contamination indicates that the backsides of substrates are being scratched during a substrate handling step or the accumulation of processing byproduct. Heretofore, however, no such integral devices or methods have been known to exist in processing systems.
Another disadvantage with conventional inspection systems is the prohibitive cost of the systems. Current systems are typically expensive stand-alone platforms that occupy clean-room space. As a result of the large area, or “footprint,” required by the stand-alone inspection platforms, the cost of owning and operating such a system is high. With regard to particle detection, the cost is further increased because of the electro-optics equipment utilized. This equipment is configured to produce high-resolution detection of small-scale particles and requires high-fidelity mechanisms, which are expensive to operate. Additionally, considerations of reduced throughput described above further increase the cost of conventional inspection systems.
Therefore, there is a need for an integrated system capable of rapidly inspecting semiconductor substrates and determining one or more conditions of the substrate in order to detect anomalies and facilitate a subsequent substrate handling decision.